1. Field of the Invention
The present invention relates to an audio and video data synchronous reproduction apparatus and method for reproducing the multiplexed stream in which audio and video data are multiplexed together with time stamps.
2. Description of the Related Art
A method for reproducing the multiplexed stream (e.g. MP4 file) in which coded audio and video data is multiplexed together with time information is proposed.
The multiplexed stream contains presentation time stamps each of which indicates, for example, the output timing of information for each audio and video frame. The time stamp is compared with the time indicated by an internal clock in a decoder, thereby determining the output timing of the decoder.
A description will be given about, for example, a voice signal. An audio decoder decodes audio data separated from the multiplexed stream. The audio decoder compares a presentation time stamp attached to each decoded audio frame with the time (generally, a counter value, which is periodically incremented) indicated by the internal clock included therein. As a result of the comparison, if the presentation time stamp is identical to or exceeds the internal time, a signal is output to an output device such as a loudspeaker.
Similarly, a video decoder decodes video data. Also in this case, the video decoder compares the presentation time stamp attached to each decoded video frame with the time indicated by the internal clock included therein. As a result of the comparison, if the presentation time stamp is identical to or exceeds the indicated time of the internal clock, a signal is output to an output device such as an LCD (Liquid Crystal Display).
If there is a pause request during reproduction, current processing on a frame is continued until the processing is finished, and the apparatus is set to a standby state. The internal clock of each decoder stops incrementing the counter value when the current processing on the frame has finished. Accordingly, the internal clock holds the internal time at which the process has finished.
In general, the time period required for decoding differs between the audio decoder and the video decoder. Accordingly, after a pause process finishes, the internal clocks of the audio and video decoders indicate different times (i.e. different counter values).
Therefore, when the pause has been released, the audio and video data may be reproduced at different points in time, since the audio and video decoders hold different internal times.
If audio and video data are reproduced at different times every time a pause is executed and released, this may annoy the user. At worst, it is possible that an initial frame immediately after the release of a pause will not be reproduced. If one or more frames are not reproduced, resultant reproduced data is incomplete. Specifically, the display may be lacking in the contents, or voice may be disjointed, which must be avoided.